OUTLINE: This is a dose-escalation, multicenter study. Patients receive intravesical gemcitabine that is left in the bladder for 2 hours and then removed on day 1. Treatment continues every 7 days for 6 courses in the absence of disease progression or unacceptable toxicity. Cohorts of 3-6 patients receive escalating doses of intravesical gemcitabine until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose preceding that at which 2 of 3 or 6 patients experience dose-limiting toxicity. Patients are followed every 3 months for 2 years, every 6 months for 2 years, and then annually thereafter.